The present invention relates to improvements to a radial cylinder hydraulic motor of the type disclosed in U.S. Pat. No. 3,828,400 which constitutes the closest known prior art and is incorporated herein by reference.
This type of motor comprises an annulus which is disposed around and integrally rotatable with a shaft. A plurality of pistons are circumferentially spaced around the annulus and are sequentially supplied with high pressure hydraulic fluid to exert driving force on the annulus and shaft in proportion to the eccentricity of the annulus. First and second pistons are disposed in diametrically opposed relation between the shaft and annulus. High pressure fluid is selectively applied to one of the first and second pistons to cause the same to move radially outwardly and vary the eccentricity of the annulus.
Although the motor functions in a satisfactory and efficient manner, it suffers from the drawback that it is capable of only two rotational speeds.
Although attempts have been made to variably position the first and second pistons and thereby the annulus by means of a servo mechanism and a fluid lock arrangement for the first and second pistons, these attempts have proven unsuccessful due to leakage from piston chambers resulting in displacement of the first and second pistons and annulus from the desired position.